This invention relates to a device for applying heat weldable modified bitumen or asphalt based rolled roofing material to roof surfaces and a method for applying the same. More specifically, this invention relates to a device and method for welding overlapping roof membranes using a flame as an heating source.
Modified bitumen or asphalt based rolled roofing material is applied to roof surfaces, particularly flat roof surfaces, to seal the roof and underlying structure from rain, snow and other natural conditions. These roofing materials are commonly available in rolls of various widths, the largest of which is 39 inches. Each roll has a length of approximately 33 feet. The common method for applying this type of material to a roof surface is to slowly unroll the material out onto the roof while manually applying heat to the undersurface of the material before it comes in contact with the roof by means of an open flame using an industrial grade propane gas torch. The undersurface of the material is heated to melting temperature. The material is then put into contact with either the roof insulation or a paper base sheet, the latter which is mechanically attached to the roof insulation prior to application of the material. When the melted material undersurface is put into contact with either the roof insulation or the base sheet, it should form a permanent watertight bond with superior strength and durability.
The open flame application method commonly used is both economical and simple, but has two serious drawbacks: (1) the danger of roof fires and personal injury; and (2) the uneven heating of the material, causing uneven bonding to the roof surface and damage to the material itself. Temperatures associated with the open flame method can exceed 2000xc2x0 F., and the danger of uncontrolled roof fires and human injury is such that many areas forbid use of this method, opting for adhesion based application systems. An adhesion based application system is safer but less desirable because it lacks the durability of the heat welded systems. Insurance premiums have skyrocketed, however, as a result of some serious accidents involving the open flame application method, resulting in some roofing contractors refusing to install this type of roofing system or to go out of business altogether. Further, uneven heating causes uneven bonding which is highly problematic when using the conventional open flame method. Not only does uneven heating ultimately decrease the durability of the welded system, but there is no way for an even highly trained and skilled roofing contractor to control the quality of the application since he cannot gauge the actual application temperature and thus be assured of optimized bonding and minimal damage to the material. In essence, the speed at which the open torch is passed over the undersurface and how quickly the material is unrolled is simply guesswork.
The industry has made a variety of attempts to resolve the problems associated with the conventional open flame application method. For instance, U.S. Pat. No. 4,743,332 to Black discloses a welding device that uses a hot plate to heat the rolled roofing material and a pressure roller to ensure adhesion to the roof surface. The problem with this device is that operationally, it involves the cumbersome process of first unrolling the desired length of rolled roofing material onto the roof surface and then feeding this material into the device via rollers which pass the material over the hot plate for melting. The other major drawback of U.S. Pat. No. 4,743,332 is that it uses an electric heating element, which is more expensive to operate than the present invention, which uses flammable gas as its source of energy. Other devices such as those described in U.S. Pat. No. 5,234,533 by Neal, U.S. Pat. No. 4,834,828 by Murphy, and U.S. Pat. No. 5,935,357 by Hubbard et at all use some type of electrical heating element rather than flammable gas.
The present invention is a device and method for welding overlapping roof materials. For purposes of this description, roof materials may be interchangeably referred to as roof membranes. The instant invention comprises a chassis, an air discharge chute and a flame distribution assembly communicating with the air discharge chute. The flame distribution assembly includes a gaseous fuel source inlet, a primary burner and an ignition source. A control unit ignites the primary burner by the ignition source. The blower connected to an inlet port of the air.discharge chute directs heat generated by the primary burner through an air discharge outlet for welding the overlapping roof membranes.
There are several advantages of the instant invention over the prior devices and methods of application. For example, this invention can eliminate the need to unroll and pre-measure the material, because the roll may be placed in a slot and unrolled as the device is operated, speeding up application time and cutting down on wasted material due to measuring inaccuracies. Further, the use of flammable gas, such as propane or butane, has a great advantage over electric heaters in that gas is economical, widely available, efficient, portable and convenient to use. Flammable gas as a source of energy for the present invention results in significant time savings because heating is instantaneous; once the invention is turned on and the gas inlet valve is opened, it can be used immediately, whereas an electrical heating element takes time to warm up and cool down. Also the present invention, unlike many of the other inventions mentioned above, can be used to apply uniform heating to the entire width of the rolled material, not to just small areas or seams.
Other embodiments of the instant invention includes a plurality of infrared temperature sensing devices located near the operator and angled to gauge the temperature of the target area between the undersurface of the rolled roof material and the interface of the weld formed therewith. The use of the temperature sensor allows the operator to accurately gauge how fast he has to pull the present invention over the roof surface to achieve an optimal bond. A light indicator can be used to signal the operator that the target area has reached the necessary welding temperature, providing better control over the welding process and assurances that heating is uniform.
This method of controlling the speed of the present invention differs substantially from that found in U.S. Pat. No. 5,072,097 by Miller, which details circuitry involved in regulating the operational speed of a welding device by measuring the temperature of the rolled roofing material as it passes over the heating plate and controlling the rate at which the material is fed through the device. More specifically, the present invention uses a simpler and more direct method of ensuring that the rolled roofing material has been sufficiently heated for proper application, by measuring the temperature directly at the area about to be welded, which is more accurate than measuring the temperature of the material as it passes over a heating element.
Accordingly, it is an object of the present invention to provide a device which is economical to use.
Another object of the present invention to provide a device which is fast and easy to operate.
It is yet another object of the present invention to provide a device which applies uniform heating to the entire width of the rolled roofing material and prevent overheating.
Still another object of the present invention is to provide a device, which is safer to use than the conventional open flame method and device.
Many other objects and features of the present invention will be obvious to those of skill in the art upon contemplation of the disclosure herein in connection with the accompanying drawings.